How Does Temporal and Sequential Delivery of Multiple Growth Factors Affect Vascularization Inside 3D Hydrogels?

Abstract

Vasculogenesis and angiogenesis are leveraged by orchestrated secretion of several growth factors. Mimicking this process in vitro can maximize vascularization inside 3D cell cultures. While the role of individual growth factors, such as vascular endothelial growth factor, Ephrin-B2, angiopoietins, and platelet-derived growth factor-BB (PDGF-BB) is well studied, the temporal influence of growth factor secretion, and the effect of their concentrations and combinations on in vitro vascularization inside hydrogels, have not been systematically investigated. Here, combinations of angiopoietin-1, angiopoietin-2, and PDGF-BB improve vascularization of a human umbilical vein endothelial cells-fibroblast coculture inside polyethylene glycol-based hydrogels the most, while the optimal concentrations and time points of growth factor addition are determined. Moreover, fibroblasts, pericytes, and mesenchymal stem cells (MSCs) are compared as supporting cells, of which MSCs best promote vascularization in coculture. Additionally, the resulting blood vessels align with magnetically oriented rod-shaped microgels when cultured inside the Anisogel. To mimic fibrosis, transforming growth factor-beta is added, resulting in significantly smaller vessels and more collagen secretion. This in vitro study reveals that a cascade of growth factors can improve vascular formation in 3D hydrogels, which is important to create viable tissue-engineered constructs for therapies and in vitro healthy and diseased tissue models.